I love the game but sometimes it doesn't convey the rules properly which results in me dying until I realize that that box can be removed by the 'z' key, controls can be a bit clunky during the action sections as well but overall a very nice game.
Like the concept, intuitive and simple. Difficulty could use a little tweaking to make some levels a little more forgiving but is still fun. Physics engine is reliable and seemingly bug-free. Art could use improvements as benjib said and sound effects too but music is good. Overall a fairly good game, keep up the good work for whatever other games you make. ;)